Communications system for addressing interferences in the communication network

ABSTRACT

A mobile communications system is described in which a mobile device is operable to communicate with base stations using a first radio technology and with other devices using a second radio technology. The mobile device maintains a control plane connection with a first base station and a user plane connection via a second base station. In case of an interference is detected due to concurrent use of the first and second radio technologies, the mobile device provides assistance information to the base stations, based on which the base stations alleviate the effects of the detected interference.

REFERENCE TO RELATED APPLICATION

The present application is a Continuation application of Ser. No.14/768,518 filed on Aug. 18, 2015, which is a National Stage Entry ofPCT/JP2014/060447 filed on Apr. 4, 2014, which claims priority fromUnited Kingdom Patent Application 1306438.1 filed on Apr. 9, 2013, thecontents of all of which are incorporated herein by reference, in theirentirety.

TECHNICAL FIELD

The present invention relates to radio access networks in a cellular orwireless telecommunications network, and particularly but notexclusively to networks operating according to the 3GPP standards orequivalents or derivatives thereof. The invention has particularalthough not exclusive relevance to the Long Term Evolution (LTE) ofUTRAN (called Evolved Universal Terrestrial Radio Access Network(E-UTRAN)) and to avoiding or reducing interference for mobile devicescommunicating with such networks; especially interference caused by, orto, non-LTE radio technologies used by the devices in addition to theLTE radio technology.

BACKGROUND ART

In a cellular communications network, mobile devices (also known as UserEquipment (UE) or mobile terminals, such as mobile telephones)communicate with remote servers or with other mobile devices via basestations. An LTE base station is also known as an ‘enhanced NodeB’(eNB). When a mobile device attaches to the LTE network via a basestation, a core network entity called Mobility Management Entity (MME)sets up a default Evolved Packet System (EPS) Bearer between the mobiledevice and a gateway in the core network. An EPS Bearer defines atransmission path through the network and assigns an IP address to themobile device to be used by the mobile device to communicate with remoteservers or other mobile devices. An EPS Bearer also has a set of datatransmission characteristics, such as quality of service, data rate andflow control parameters, which are defined by the subscriptionassociated with the mobile device and are established by the MME uponregistration of the mobile device with the network.

The EPS Bearer is thus managed by the MME, which signals to the mobiledevice when it needs to activate, modify, or deactivate a particular EPSBearer. Thus there are two connections between the mobile device and thecommunication network: one for the user data transmitted using theestablished EPS bearer (also known as the user plane or U-plane) andanother one for managing the EPS Bearer itself (also known as thecontrol plane or C-plane)

In their communication with each other, mobile devices and base stationsuse licensed radio frequencies, which are typically divided intofrequency bands and/or time blocks. Depending on various criteria (suchas the amount of data to be transmitted, radio technologies supported bythe mobile device, expected quality of service, subscription settings,etc.), each base station is responsible for controlling the transmissiontimings, frequencies, transmission powers, modulations, etc. employed bythe mobile devices attached to the base station. In order to minimisedisruption to the service and to maximise utilisation of the availablebandwidth, the base stations continuously adjust their own transmissionpower and also that of the mobile devices. Base stations also assignfrequency bands and/or time slots to mobile devices, and also select andenforce the appropriate transmission technology to be used between thebase stations and the attached mobile devices. By doing so, basestations also reduce or eliminate any harmful interference caused bymobile devices to each other or to the base stations.

In order to optimise utilisation of their bandwidth, LTE base stationsreceive periodic signal measurement reports from each served mobiledevice, which contain information about the perceived signal quality ona given frequency band used by (or being a candidate frequency band for)that mobile device. These signal measurement reports are then used bythe base stations in their decision to allocate certain parts of theirbandwidth to the served mobile devices and also to hand over mobiledevices to other base stations (or other frequency bands/other radioaccess technologies (RATs)) when the signal quality does not meet theestablished criteria. The handing over of a mobile device might benecessary, for example, when the mobile device has moved away from thegiven base station, and also when an interference problem has arisen.

Current mobile devices typically support multiple radio technologies,not only LTE. The mobile devices might include, for example,transceivers and/or receivers operating in the Industrial, Scientificand Medical (ISM) radio bands, such as Bluetooth or Wi-Fi transceivers.Furthermore, mobile devices might also include positioning functionalityand associated circuitry, for example Global Navigation Satellite System(GNSS) transceivers and/or receivers. Both ISM and GNSS (hereaftercommonly referred to as non-LTE) radio technologies use frequency bandsclose to or partially overlapping with the LTE frequency bands. Some ofthese non-LTE frequency bands are licensed for a particular use (e.g.Global Positioning Systems (GPS) bands) or might be unlicensed bands andcan be used by a number of radio technologies (such as Bluetooth andWi-Fi standards using the same range of ISM frequency bands). The mannerin which these non-LTE frequency bands are used are, therefore, notcovered by the LTE standards and are not controlled by the LTE basestations. However, transmissions in the non-LTE frequency bands might,nevertheless, still cause undesired interference to (or suffer undesiredinterference resulting from) transmissions in the LTE bands,particularly in the overlapping or neighbouring frequency bands.

Such non-LTE radio technologies might be used by the mobile deviceitself or by other mobile devices in their vicinity and, although theseradio technologies conform to the relevant standards (i.e. other thanLTE), might still cause undesired interference to (or sufferinterference from) the LTE transmission of these mobile devices. This isespecially true when the end user is operating an ISM transceiver inparallel with the LTE transceiver, for example when the user is making avoice over IP (VoIP) call using a Bluetooth headset. It will beappreciated that in this case the LTE and ISM transmissions willinterfere with each other as the LTE voice data received from the basestation is relayed to the headset using the ISM transceiver implementedin the same mobile device. Thus any signal quality measurementsperformed by this mobile device before the VoIP call would notcorrespond to the actual signal quality perceived during the call.Furthermore, since an LTE base station can control only the mobiledevice's (and its own) LTE transmissions, any corrective measures madeby the base station would inevitably fail to improve the interferenceperceived by the mobile device because of the concurrently operated ISMtransceiver.

In another typical scenario, the LTE transceiver of the mobile devicecan cause interference to the GNSS receiver (e.g. a GPS receiver) makingit difficult to obtain a current location of the mobile device. In thiscase, although there is no apparent disruption to the LTE signal (thesignal quality measurements by the mobile device would indicateacceptable signal conditions), the LTE transmissions by the mobiledevice would be likely to render the GNSS functionality unusable becauseof the interference caused by the LTE transceiver to the GNSS receiverof the mobile device.

When interference such as this arises as a result of communicationoccurring concurrently in the same mobile device (for example,concurrent use of LTE and non-LTE radio technologies) the interferenceis sometimes referred to as ‘in-device coexistence (IDC) interference’which causes an ‘in-device coexistence (IDC) situation’.

For mobile devices using the standard frequency bands simultaneously forLTE and ISM/GNSS radio communications, the typical in-device coexistencescenarios include:

-   -   LTE Band 40 radio transmitter causing interference to ISM radio        receiver;    -   ISM radio transmitter causing interference to LTE Band 40 radio        receiver;    -   LTE Band 7 radio transmitter causing interference to ISM radio        receiver;    -   LTE Band 7/13/14 radio transmitter causing interference to GNSS        radio receiver.

However, other bands and/or other radio technologies might alsoexperience interference due to LTE/ISM/GNSS transmissions.

In order to be able to alleviate the problems due to IDC interference,the mobile device indicates its IDC capability to its serving basestation. If the received IDC capability of the mobile device indicatesthat the mobile device is able to do so, the serving base stationconfigures the mobile device (by providing so-called ‘idc-config’settings) to address IDC interference autonomously. Therefore, when themobile device experiences interference due to an IDC situation, it canadjust its LTE and/or non-LTE transmissions in accordance with the‘idc-config’ settings, thereby reducing or eliminating the experiencedinterference. In particular, the mobile device is allowed by the networkto ‘deny’ (i.e. suspend or delay) its (already scheduled and henceexpected) LTE transmissions up to a limit/rate specified in the‘idc-config’ parameters. Essentially, this allows the mobile telephoneto temporarily override the LTE scheduling decisions made by the networkand to carry out ISM signalling and whilst its LTE transmissions are‘autonomously’ suspended.

However, some IDC interference situations cannot be solved by the mobiledevice by itself, even if an ‘idc-config’ has been provided by the basestation. In this case, the mobile device may need to send an IDCindication to the network (e.g. in an uplink RRC message) to inform thenetwork about the IDC situation. To address such situations, 3GPPstandards provide three techniques, using which the network (i.e. an LTEbase station) is able to provide a solution when the mobile devicecannot solve the problem by itself. The three techniques comprise: a TDM(Time Division Multiplexing) solution, an FDM (Frequency DivisionMultiplexing) solution, and a Power Control solution. It will beappreciated that ‘solution’ as used herein refers to control and/orconfiguration data that may be used by the mobile device to eliminate,or at least mitigate, the effects of the detected interference.

The TDM solution ensures that the transmission of a radio signal doesnot coincide with the reception of another radio signal. The FDMsolution consists of choosing another serving frequency for the mobiledevice than the one suffering from interference. The Power Controlsolution aims to reduce radio transmission power to mitigate the effectof interference.

In order to benefit from these techniques, if the mobile device detectsthat an IDC situation is causing interference, it informs the basestation (e.g. using Radio Resource Control (RRC) layer signalling) thatan IDC situation has arisen and it provides assistance information(sometimes referred to as an ‘IDC assistance indication’) using whichthe base station is able to select the most appropriate technique toaddress the interference caused by the IDC situation. For example, thebase station may select a different frequency for the mobile deviceindicating the IDC situation (FDM solution). Alternatively, the basestation may reconfigure the transmission (e.g. apply discontinuousreception (DRX) and/or change its subframe pattern) (TDM solution) forthat mobile device. The base station may also adjust its (or initiateadjustment of the mobile device's) transmission power (Power Controlsolution).

Further details of these techniques can be found in section 23.4 of the3GPP TS 36.300 standards document (v.11.5.0). Details of the‘idc-config’ settings can be found in the 3GPP TS 36.331 standardsdocument (v.11.3.0). The contents of both documents are incorporatedherein by reference.

However, the above solutions are not always applicable for the so-calledsmall cell enhancement scenarios defined in 3GPP TR 36.932 (v.12.1.0).‘Small cells’ in this context refer to the coverage areas of low-powernodes (for example Pico eNBs or Femto eNBs) that are being consideredfor LTE in order to support mobile traffic explosion, especially forindoor and outdoor hotspot deployments. A low-power node generallyrefers to a node that is operating a cell (‘small cell’) with a typicaltransmit power which is lower than typical transmit powers used in cellsof macro nodes and base stations (‘macro cells’).

In particular, some of the small cell enhancement scenarios are based ona split control-plane/user-plane architecture (referred to as ‘C/USplit’), in which the mobile device is configured to maintain itscontrol plane connection with the communication network via a macro cell(operating as a primary cell or ‘Pcell’) and at the same time maintainits user plane connection via one or more ‘small cells’ (operating assecondary cell or ‘Scell’) and thereby reducing the load in the macrocell. Effectively, in this case the mobile device is using two separateradio connections via two separate nodes (i.e. a macro base station anda low-power node), one for sending/receiving user data, and another onefor controlling the mobile device's operations, such as mobilitymanagement, security control, authentication, setting up ofcommunication bearers, etc.

In such situations, interference may occur on either radio connection.However, the mobile device is configured to receive its ‘idc-config’settings (if any) from the macro base station, which settings areadapted to handle IDC situations arising in the macro cell (whichcarries the control plane only, in case of C/U-plane split) and thuscannot be used to tackle user plane interference experienced in thesmall cell. Even if the ‘idc-config’ would be adapted and/or applied tosmall cells (or both macro cells and small cells), due to the relativelylarge number of small cells, and their possibly differing operatingcharacteristics (compared to the macro cell and also to other smallcells), such ‘idc-config’ would not be capable of addressing all thedifferent possible IDC situations.

Furthermore, the mobile device can only send an IDC assistanceindication to the macro base station (via which it has a control planeconnection), not the low-power node handling its user plane connection.However, given the relatively lower transmit power level used by thelow-power node, user plane transmissions via the small cell might bemore sensitive to interference than control plane transmission via themacro cell.

Even in the case when the mobile device experiences interference on thecontrol plane and notifies this to the macro base station, any change inthe macro base station's operation may cause unexpected interference forthe user plane connection via the small cell.

There is therefore a need to improve the operation of the mobile device,the base station, and the low-power node in order to overcome or atleast alleviate the above problems.

SUMMARY OF INVENTION

Embodiments of the present invention aim to provide improved techniquesfor alleviating interference in a communications network and, inparticular, for alleviating radio interference caused to, or by,transmissions between a mobile communication device and nodes of amobile (cellular) communication.

In one aspect, the present invention provides a mobile devicecomprising: first communicating means for communicating with a first anda second base station using a first radio technology; secondcommunicating means for communicating with a wireless communicationsdevice using a second radio technology; means for detecting interferencearising as a result of coexistence of said first and second radiotechnologies within said mobile device; providing means for providing,to said first base station and responsive to detecting said interferencearising as a result of said coexistence, coexistence informationidentifying at least one parameter associated with communicating withsaid second base station; and receiving means for receiving from atleast one of said first and second base stations, responsive toproviding said coexistence information, control information foralleviating said interference; wherein said first communicating means isoperable to control communication with the first and/or the second basestations, based on said control information, whereby to alleviate thedetected interference.

The first communicating means may be operable to communicate controldata via said first base station and to communicate user data via saidsecond base station. In this case, the first communicating means may befurther operable to communicate user data via said first base station.

The first communicating means may be operable to communicate controldata and user data via said first base station and to elect said secondbase station as a candidate for communicating user data. In this case,said control information for alleviating said interference may comprisecontrol data causing said first communicating means to continuecommunicating control data and user data via said first base station.Alternatively, the first communicating means may be operable to elect adifferent base station than said second base station as a candidate forcommunicating user data.

The control data may cause said first communicating means to alleviatethe detected interference by applying a frequency division multiplexing(FDM) solution. In this case, the control information for alleviatingsaid interference may comprise control data causing said firstcommunicating means to communicate user data via a different basestation than said second base station. For example, the different basestation may be the first base station.

The control data may cause said first communicating means to alleviatethe detected interference by applying a time division multiplexing (TDM)solution. In this case, the control information for alleviating saidinterference may comprise control data causing said first communicatingmeans to prevent communication of user data and/or control data whilstsaid second communicating means is communicating with said wirelesscommunications device using said second radio technology.

The providing means may be operable to provide said coexistenceinformation to said first base station and the receiving means may beoperable to receive said control information via said second basestation.

The mobile device may further comprise means for providing informationrelating to a capability of the mobile device to address in-devicecoexistence interference and the control information for alleviatingsaid interference may be dependent on said capability of the mobiledevice.

The providing means for providing coexistence information and thereceiving means for receiving control information may be operable toexchange Radio Resource Control (RRC) messages with the base station.

The first radio technology may be a radio technology according to theLong Term Evolution (LTE) standard. The second radio technology may be aradio technology according to any one of the Bluetooth, Wi-Fi, and GPSstandards.

In another aspect, the invention provides a mobile device comprising atransceiver and a processor, wherein: said transceiver is configured to:communicate with a first and a second base station using a first radiotechnology; and communicate with a wireless communications device usinga second radio technology. The processor is configured to detectinterference arising as a result of coexistence of said first and secondradio technologies within said mobile device. The transceiver isconfigured to: provide, to said first base station and responsive todetecting said interference arising as a result of said coexistence,coexistence information identifying at least one parameter associatedwith communicating with said second base station; and receive from atleast one of said first and second base stations, responsive toproviding said coexistence information, control information foralleviating said interference. The transceiver communicating using saidfirst radio technology is operable to control communication with thefirst and/or the second base stations, based on said controlinformation, whereby to alleviate the detected interference.

In yet another aspect, the invention provides a base station comprising:communicating means for communicating with a mobile device using a firstradio technology; means for exchanging control data with another basestation relating to said mobile device; receiving means for receiving,from said mobile device, an indication that interference has arisen as aresult of coexistence of said first radio technology and a second radiotechnology in said mobile device, said indication comprising coexistenceinformation identifying at least one parameter associated withcommunicating with said other base station; means for generating controlinformation for alleviating said interference between said first andsecond radio technologies based on said coexistence information; andsending means for sending the generated control information to themobile device to alleviate the interference.

The control information may comprise configuration data. For example,the configuration data may comprise an in-device coexistenceconfiguration data (e.g. ‘idc-config’ data). The control information mayalso comprise an instruction to modify an operating parameter of thefirst and/or the second radio technology.

The communicating means may be operable to communicate control data forsaid mobile device via said first base station and to communicate userdata for said mobile device via said second base station. In this case,the communicating means may be further operable to communicate user datafor said mobile device via said first base station.

The communicating means may be operable to communicate control data anduser data for said mobile device via said first base station and toelect said second base station as a candidate for communicating userdata for said mobile device. In this case, the communicating means maybe operable to continue communicating control data and user data forsaid mobile device via said first base station. Alternatively, thecommunicating means may be operable to elect a different base stationthan said second base station as a candidate for communicating user datafor said mobile device.

The control data may cause said mobile device to alleviate the detectedinterference by applying a frequency division multiplexing (FDM)solution. In this case, the control information for alleviating saidinterference may comprise control data causing said communicating meansto communicate user data via a different base station than said secondbase station. For example, the different base station may be said firstbase station.

The control data may cause said mobile device to alleviate the detectedinterference by applying a time division multiplexing (TDM) solution. Inthis case, the control information for alleviating said interference maycomprise control data causing said mobile device to preventcommunication of user data and/or control data whilst said mobile deviceis communicating with said wireless communications device using saidsecond radio technology.

The control information may comprise an autonomous denial rate (ADR)configuration. In this case, the ADR configuration may be forcommunications via said second base station.

The control information may comprise a discontinuous reception (DRX)configuration. In this case, the DRX configuration may be forcommunications via said second base station.

The control information may comprise a hybrid automatic retransmissionrequest (HARQ) configuration. In this case, the HARQ configuration maybe for communications via said second base station.

The receiving means may be operable to receive said coexistenceinformation directly from said mobile device and said sending means maybe operable to send said control information to said mobile device viasaid second base station.

The base station may further comprise obtaining means for obtaininginformation relating to a capability of the mobile device to addressin-device coexistence interference and the control information foralleviating said interference may be dependent on said capability of themobile device.

The obtaining means may be operable to obtain said capabilityinformation form said second base station. The obtaining means may alsobe operable to obtain said capability information form said mobiledevice. In this case, the obtaining means may be operable to obtain saidcapability information form said mobile device via said second basestation.

The obtaining means may be operable to receive said capabilityinformation in at least one message. The at least one message includesat least one information element (IE) selected from the followinginformation elements: an information element comprising an indication ofa capability of said second base station (e.g. a ‘Pico IDC Capabilty’IE), an information element comprising parameters for an autonomousdenial functionality (e.g. an ‘Autonomous Denial Parameters’ IE), aninformation element comprising assistance information for said mobiledevice (e.g. a ‘UE Assistance Information’ IE), an information elementcomprising a DRX configuration for said mobile device to be applied fora cell of said first base station (e.g. a ‘drx-config_Pcell’ IE), aninformation element comprising a DRX configuration for said mobiledevice to be applied for a cell of said second base station (e.g. a‘drx-config_Scell’ IE), an information element comprising a sub-framepattern for said mobile device (e.g. a ‘Sub-frame Pattern’ IE), and aninformation element comprising TDM assistance information for saidmobile device to be applied for a cell of said second base station (e.g.a ‘Tdm-AssistanceInformationScell’ IE).

The receiving means for receiving said coexistence information and thesending means for sending said control information may be operable toexchange Radio Resource Control (RRC) messages with the mobile device.

In a further aspect, the invention provides a base station comprising atransceiver and a processor, wherein: said transceiver is configured to:communicate with a mobile device using a first radio technology;exchange control data with another base station relating to said mobiledevice; receive, from said mobile device, an indication thatinterference has arisen as a result of coexistence of said first radiotechnology and a second radio technology in said mobile device, saidindication comprising coexistence information identifying at least oneparameter associated with communicating with said other base station.The processor is configured to generate control information foralleviating said interference between said first and second radiotechnologies based on said coexistence information; and the transceiveris configured to send the generated control information to the mobiledevice to alleviate the interference.

The invention also provides a system comprising the above describedmobile device, the first base station, and the other base station.

In a further aspect, the invention provides a method performed by amobile device configured to communicate with a first and a second basestation using a first radio technology and to communicate with awireless communications device using a second radio technology, themethod comprising: detecting interference arising as a result ofcoexistence of said first and second radio technologies within saidmobile device; providing, to said first base station and responsive todetecting said interference arising as a result of said coexistence,coexistence information identifying at least one parameter associatedwith communicating with said second base station; and receiving from atleast one of said first and second base stations, responsive toproviding said coexistence information, control information foralleviating said interference; wherein said communicating using saidfirst radio technology is arranged to control communication with thefirst and/or the second base stations, based on said controlinformation, whereby to alleviate the detected interference.

The invention also provides a method performed by a base stationconfigured to communicate with a mobile device using a first radiotechnology, the method comprising: exchanging control data with anotherbase station relating to said mobile device; receiving, from said mobiledevice, an indication that interference has arisen as a result of thecoexistence of said first radio technology and a second radio technologyin said mobile device, said indication comprising coexistenceinformation identifying at least one parameter associated withcommunicating with said other base station; generating controlinformation for alleviating said interference between said first andsecond radio technologies based on said coexistence information; andsending the generated control information to the mobile device toalleviate the interference.

Aspects of the invention extend to computer program products such ascomputer readable storage media having instructions stored thereon whichare operable to program a programmable processor to carry out a methodas described in the aspects and possibilities set out above or recitedin the claims and/or to program a suitably adapted computer to providethe apparatus recited in any of the claims.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments of the invention will now be described, by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 schematically illustrates a mobile telecommunication system of atype to which the invention is applicable;

FIG. 2 schematically illustrates an example deployment scenario of themobile telecommunication system of FIG. 1;

FIG. 3 schematically illustrates various radio transceiver circuitsimplemented on a mobile device of the mobile telecommunication systemshown in FIG. 1;

FIG. 4 is a block diagram of a mobile device forming part of the mobiletelecommunication system shown in FIG. 1;

FIG. 5 is a block diagram of a macro base station forming part of themobile telecommunication system shown in FIG. 1;

FIG. 6 is a block diagram of a low-power node forming part of the mobiletelecommunication system shown in FIG. 1;

FIG. 7 is an overview of protocol stacks for implementing split controlplane/user plane functionality by the elements of the mobiletelecommunication system shown in FIG. 1; and

FIG. 8 is an exemplary flowchart illustrating a method performed by thebase station forming part of the mobile telecommunication system shownin FIG. 1.

MODE FOR CARRYING OUT THE INVENTION

Overview

FIG. 1 schematically illustrates a mobile (cellular) telecommunicationsystem 1 in which users of mobile devices 3 (for example mobiletelephones) can communicate with other users via each of a plurality ofbase stations 5-1, 5-2 and a core network 7. In the system illustratedin FIG. 1, the base station 5-1 is a macro base station and the basestation 5-2 is a pico base station (or other low-power node). Furtherbase stations (not shown) might operate according to differentstandards, such as the Wideband Code Division Multiple Access (W-CDMA)or the GSM (Global System for Mobile Communications) EDGE (Enhanced Datarates for GSM Evolution) Radio Access Network (GERAN) standards or thelike.

The core network 7 comprises a mobility management entity (MME) 12, aserving gateway (SGW) 14, and a PDN gateway (PGW) 16.

Each base station 5 operates at least one base station cell, each havinga number of uplink and downlink communications resources (channels,sub-carriers, time slots, etc.) that are available for wirelesscommunication between the mobile device 3 and the corresponding basestation 5. In this exemplary embodiment, it will be assumed, for thesake of simplicity of explanation, that the mobile device 3 has one userplane connection and one control plane connection with two respectivebase stations 5, although, in deployed systems, a mobile device 3 mighthave multiple user plane connections and multiple control planeconnections with several base stations in parallel. In this example, theRadio Access Technologies (RATs) employed by the base stations 5 operateaccording to either Frequency Division Duplexing (FDD) or Time DivisionDuplexing (TDD).

In TDD, the time domain of a communication channel (of a base station 5)is divided into several recurrent time slots of fixed length in whichcommunication to/from the base station 5 can be scheduled. In operationin TDD, two or more data streams may be transferred between the basestation 5 and the mobile device(s) 3, apparently simultaneously, insub-channels of one communication channel, by scheduling each datastream in different time slots of the channel (effectively ‘takingturns’). In FDD, the bandwidth available to the base station 5 isdivided into a series of non-overlapping frequency sub-bands eachcomprising frequency resources that may be assigned to mobile devices 3for communication via the base station 5.

The serving base station 5 allocates downlink resources to the mobiledevice 3 depending on the amount of data to be sent to the device.Similarly, the base station 5 allocates uplink resources to the mobiledevice 3 depending on the amount and type of data the mobile device 3has to send to the base station 5. The uplink and downlink resourcestypically comprise physical resource blocks (PRBs) which are blocks offrequency resources in the frequency range used by that particular basestation 5.

During allocation of uplink and downlink resources, the serving basestation 5 also takes into account the signal quality available on thegiven frequency used by (or allocated to) the mobile device 3. Theserving base station 5 allocates PRBs to the mobile device 3dynamically, also taking into account the current transmission needs andsignal conditions (as reported by the mobile device 3). Base stations 5generally aim to maximise usage of the available bandwidth so that eachmobile device 3 that they are serving has sufficient transmissionopportunity, communicates at its optimum transmission power, and doesnot cause interference to the other mobile devices 3 or to the basestations 5.

In this exemplary embodiment, initially, the mobile device 3 isconnected to the macro base station 5-1 only, either having a controlplane connection only (e.g. in an initial phase of attachment to thecommunication network) or having both its control plane and user planeconnections set up via the macro base station 5-1. However, the mobiledevice 3 is capable to use separate control plane and user planeconnections (C/U Split) with the macro base station 5-1 and the picobase station 5-2, respectively. The C/U Split functionality may betriggered by the macro base station 5-1 e.g. due to current networkload, signal conditions reported by the mobile device 3, etc. Therefore,when the macro base station 5-1 determines that C/U Split functionalitywould be favourable (and that it is supported by the mobile device 3),the macro base station 5-1 selects a suitable low-power node (such asthe pico base station 5-2) and sets up a new (or moves the existing)user plane connection for that mobile device 3 to the selected node 5-2(but keeps the control plane connection for this mobile device 3 routedvia itself). An exemplary deployment scenario of a mobiletelecommunication system having a plurality of low-power nodes is shownin FIG. 2. In this exemplary scenario, the macro base station 5-1 mayselect the pico base station 5-2 as indicated, if it determines that thecell of this pico base station 5-2 is accessible to the mobile device 3(i.e. it is within its range, uses compatible technology, has beenauthorised to use, etc.).

Referring to FIG. 1 again, the mobile device 3 is also capable ofcommunicating using non-LTE radio technologies such as those which useresources of the Industrial, Scientific and Medical (ISM) frequencybands. For example, the mobile device 3 can communicate with a Wi-Fiaccess point 8 of a Wireless Local Area Network (WLAN) (not shown)operating according to one of the 802.11 family of standards defined bythe Institute of Electrical and Electronics Engineers (IEEE). The mobiledevice 3 can also communicate with a wireless headset 9 operatingaccording to e.g. the Bluetooth standard defined by the BluetoothSpecial Interest Group (SIG). In addition, the mobile device 3 alsosupports positioning technologies and thus communicates with, forexample, a positioning satellite 10 using GPS signals.

Communications between the mobile device 3 and the access point 8, thewireless headset 9, and/or the positioning satellite 10 might occursubstantially concurrently with the communication between the mobiledevice 3 and the base station(s) 5, which concurrent communication hasthe potential to cause undesirable interference (i.e. IDC interference).

The issue of IDC interference is illustrated further in FIG. 3 whichschematically illustrates, purely illustratively, the various radiotransceiver circuits implemented on a mobile device 3 shown in FIG. 1.

As shown in FIG. 3, the mobile device 3 comprises an LTE basebandcircuit 300 a, a GNSS baseband circuit 300 b, and an ISM basebandcircuit 300 c. Each baseband circuit 300 a to 300 c is coupled to aradio frequency (RF) transceiver (or receiver), i.e. LTE transceiver 301a, GNSS transceiver 301 b, and ISM transceiver 301 c, respectively.Communications in the LTE band are carried out using an LTE antenna 303a. Similarly, communications in the non-LTE bands are carried out usingthe respective GNSS antenna 303 b and/or the ISM antenna 303 c.

As indicated by dashed arrows in FIG. 3, any of the transceivers 301 ato 301 c might suffer interference from either one of the othertransceivers operating in the same mobile device 3.

Advantageously, the mobile device 3 and the base stations 5 areconfigured to co-operate to alleviate any such in-device coexistence(IDC) interference.

The mobile device 3 detects the IDC interference and, after establishinginformation about the nature of the interference the mobile device 3initially attempts to deal with the interference itself, for example bymodifying the timings of the LTE and/or non-LTE radio communications ina time-based solution (as prescribed in its ‘idc-config’ settings, ifavailable). If this is not sufficiently successful, however, the mobiledevice 3 generates IDC assistance information and communicates thegenerated assistance information to the macro base station 5-1, toassist the base stations 5 to take appropriate corrective action forreducing or eliminating the interference. Advantageously, the mobiledevice 3 includes in the IDC assistance information an indication ofwhether the interference is related to the control plane and/or the userplane, which cell and which frequency (or frequency band) isexperiencing interference, whether any autonomous corrective actionshave been applied by the mobile device 3, and so on. To the extentnecessary, this information is shared between the macro base station 5-1and the pico base station 5-2 in order to successfully alleviateinterference in both their cells. In addition to this information, themacro base station 5-1 and the pico base station 5-2 also share witheach other information relating to their capabilities, preferences,operating parameters, and so on. Beneficially, in this example, suchbase station specific information is shared before C/U Splitfunctionality is invoked for a particular mobile device 3, e.g. as partof regular connection setup/maintenance procedure between the basestations 5.

Therefore, in this system, the macro base station 5-1 is able to takeinto account any IDC indication provided by the mobile device 3 and alsoany information provided by the pico base station 5-2 when managing(e.g. setting up, terminating, reconfiguring) the C/U Splitfunctionality for that device. The macro base station 5-1 exchangesinformation with the pico base station 5-2 operating as a current (orcandidate) low-power node for carrying user plane signalling for themobile device 3. The information exchanged between the macro basestation 5-1 and the pico base station 5-2 may include, for example,information about the capabilities of the mobile device 3, informationabout the capabilities of the pico base station 5-2, information aboutthe configuration of the pico base station 5-2 (such as acurrent/preferred/optimal configuration), ‘idc-config’ settings for themobile device 3, IDC indication (or part thereof) received from themobile device 3, control data for controlling the pico base station 5-2and/or the mobile device 3, etc.

Since the information (other than the IDC indication received from themobile device 3) is exchanged between the base stations 5 using the X2interface provided between them, utilisation of the air interfaceresources can be optimised. However, since the macro base station 5-1 isaware of any existing IDC situation and also the capabilities andsettings of both the mobile device 3 and the pico base station 5-2, itcan determine the appropriate course of action, and address any IDCinterference (regardless whether it is detected for the macro cell orthe small cell) in a timely manner and without added complexity to themobile device 3.

Using the above approach, interference in small cells can be avoidedeven when the control plane is routed via a different cell (the macrocell). Even in the rare case when it is not possible to completely avoidinterference for a user device in a small cell, the pico base station(low-power node) 5-2 operating that small cell can be informed about anyarising IDC interference and hence it can mitigate the effect of thatinterference with minimum disturbance to the user plane connection forthe mobile device (user device) 3.

Mobile Device

FIG. 4 is a block diagram of a mobile device 3 forming part of themobile telecommunication system 1 shown in FIG. 1. As shown, the mobiledevice 3 includes transceiver circuits 301 a to 301 c which are operableto transmit signals to and to receive signals from the base station 5via one or more antennas 303 a to 303 c. The mobile device 3 alsoincludes a user interface 305 that is controlled by a controller 307 andwhich allows a user to interact with the mobile device 3.

The controller 307 controls the operation of the transceiver circuits301 a to 301 c in accordance with software and data stored in memory309. The software includes, among other things, an operating system 311,an LTE module 313, an ISM module 315, a GNSS module 317, an interferencedetection module 319, and a reporting module 321.

The LTE module 313 is operable to control the communications of themobile device 3 using the LTE radio technologies. The LTE module 313receives instructions from the base station 5 (via the LTE transceivercircuit 301 a and the LTE antenna 303 a) and stores them in the memory309. Based on the received instructions, the LTE module 313 is operableto select the appropriate frequency band, transmission power, modulationmode etc. used in the LTE communications. The LTE module 313 is alsooperable to update the base station 5 about the amount and type ofuplink and/or downlink data scheduled for transmission in order toassist the base station 5 in allocating resources among the mobiledevices it is serving.

The ISM module 315 is operable to control the ISM communications of themobile device 3. In doing so, the ISM module 315 might, for example, usedata received from the access point 8 and/or communicate with thewireless headset 9.

The GNSS module 317 is operable to obtain a current geographic locationof the mobile device 3 and to control the GNSS communications of themobile device 3. In doing so, the GNSS module 317 might, for example,use data received from the positioning satellite 10.

Apart from the received control data, default control parameters arestored in the memory 309 and might be used by any of the LTE/ISM/GNSSmodules 313 to 317 to control communications of the mobile device 3 asappropriate.

The interference detection module 319 is operable to detect interferencecaused to communications by the LTE module 313, the ISM module 315, andthe GNSS module 317. In particular, the interference detection module319 is operable to detect interference that has arisen due to coexistingcommunications by any of the LTE module 313, the ISM module 315, and theGNSS module 317. The interference detection module 319 may detectinterference, e.g. by performing signal measurements, such as referencesignal received power (RSRP), received power received quality (RSRQ)measurements, and the like. The interference detection module 319 mayalso detect interference by monitoring operation of the transceivercircuits 301 a to 301 c, for example to establish a measure of bit rate(or error rate, error count) for communications using the transceivercircuits 301 a to 301 c. The measured bit rate(s) might be establishedseparately for uplink and downlink.

The reporting module 321 is operable to generate and send IDC assistanceinformation to the base station 5. In order to do so, the reportingmodule 321 is operable to obtain data from the LTE module 313, the ISMmodule 315, the GNSS module 317, and/or the interference detectionmodule 319 as appropriate. The reporting module 321 indicates theoccurrence of in-device interference by sending an associated message tothe base station 5 via the LTE transceiver circuit 301 a. In thisexemplary embodiment the message comprises a dedicated radio resourcecontrol (RRC) message (e.g. an RRC InDeviceCoexistence Indicationmessage or the like) although any appropriate signalling may be used.

Macro Base Station

FIG. 5 is a block diagram of a macro base station 5-1 forming part ofthe mobile telecommunication system 1 shown in FIG. 1. As shown, themacro base station 5-1 includes a transceiver circuit 501 which isoperable to transmit signals to and to receive signals from the mobiledevices 3 via one or more antennas 503 and to transmit signals to andreceive signals from the core network 7 and other base stations 5 (suchas the pico base station 5-2) via a network interface 505 (which may bea copper or optical fibre interface). A controller 507 controls theoperation of the transceiver circuit 501 in accordance with software anddata stored in memory 509. The software includes, among other things, anoperating system 511, a communications control module 513, aninterference management module 515, and a scheduler module 517.

The communications control module 513 controls communications betweenthe macro base station 5-1 and external devices via the transceivercircuitry 501 and the one or more antenna 503.

The interference management module 515 receives and handles theassistance information from the mobile devices 3. The interferencemanagement module 515 also obtains the information relating to thecapabilities, preferences, operating parameters of neighbouring basestations 5 (such as pico base station 5-2) which is then stored inmemory 509. The interference management module 515 is also operable todetermine, based on the obtained assistance information and theinformation obtained from the neighbouring base stations 5, appropriateaction to be taken to reduce IDC interference at the mobile device 3 forexample by managing the allocation of time and/or frequency resources tothe mobile devices 3 served by this macro base station 5-1 and/or by thepico base station 5-2 (in case of C/U Split is in place).

The scheduler module 517 is operable to receive and process requestsfrom the mobile devices 3 for allocation of uplink and downlinkresources. The scheduler module 517 is also operable to obtaininformation from the interference management module 515 identifying anyinterference reduction actions and takes these into account whenallocating resources to the affected mobile devices 3.

Pico Base Station

FIG. 6 is a block diagram of a pico base station 5-2 forming part of themobile telecommunication system 1 shown in FIG. 1. As shown, the picobase station 5-2 includes a transceiver circuit 601 which is operable totransmit signals to and to receive signals from the mobile devices 3 viaone or more antennas 603 and to transmit signals to and receive signalsfrom the core network 7 and other base stations 5 (such as the macrobase station 5-1) via a network interface 605 (which may be a copper oroptical fibre interface). A controller 607 controls the operation of thetransceiver circuit 601 in accordance with software and data stored inmemory 609. The software includes, among other things, an operatingsystem 611, a communications control module 613, an interferencemanagement module 615, and a scheduler module 617.

The communications control module 613 controls communications betweenthe macro base station 5-1 and external devices via the transceivercircuit 601 and the one or more antenna 603.

The interference management module 615 receives and handles theassistance information from the mobile devices 3 (either directly or viathe macro base station 5-1). The interference management module 615 alsoobtains the information relating to the capabilities, preferences,operating parameters of neighbouring base stations 5 (such as macro basestation 5-1) which is then stored in memory 609. The interferencemanagement module 615 is also operable to determine, based on theobtained assistance information and the information obtained from theneighbouring base stations 5, appropriate action to be taken to reduceIDC interference at the mobile device 3 for example by managing theallocation of time and/or frequency resources to the mobile devices 3served by this pico base station 5-2.

The scheduler module 617 is operable to receive and process requestsfrom the mobile devices 3 for allocation of uplink and downlinkresources. The scheduler module 617 is also operable to obtaininformation from the interference management module 615 identifying anyinterference reduction actions and takes these into account whenallocating resources to the affected mobile devices 3.

In the above description, the mobile device 3 and the base stations 5are described for ease of understanding as having a number of discretemodules (such as the communications control modules and the LTE/ISM/GNSSmodules). Whilst these modules may be provided in this way for certainapplications, for example where an existing system has been modified toimplement the invention, in other applications, for example in systemsdesigned with the inventive features in mind from the outset, thesemodules may be built into the overall operating system or code and sothese modules may not be discernible as discrete entities.

Operation

FIG. 7 is an overview of the elements of the telecommunication systemshown in FIG. 1 for implementing split control plane/user planefunctionality. FIG. 7 also shows the respective protocol stacks of thesenetwork elements.

As can be seen in this figure, control plane connection is providedbetween the MME 12 and the macro base station 5-1 using S1-MMEsignalling (via the S1 interface) and between the macro base station 5-1and the mobile device 3 using RRC signalling (via the air interface).

On the other hand, user plane connection is provided between the corenetwork 7 and the pico base station 5-2 (via the S1 interface) andbetween the pico base station 5-2 and the mobile device 3 via the airinterface (which is different than the one used for the control plane).Alternatively, if the pico base station 5-2 is not connected directly tothe core network 7, Internet Protocol (IP) tunnelling may be usedbetween the PGW 16 (FIG. 1) and the pico base station 5-2, e.g. via aNon 3GPP network.

The macro base station 5-1 and the pico base station 5-2 can communicatewith each other via the X2 interface, for example, to exchange basestation specific configurations and/or control data.

An S5/S8 interface is provided between the MME 12 and the SGW 14 inorder to manage the routing of user plane data through the core network7.

In this kind of architecture, at least the following scenarios mayresult in an IDC interference problem:

-   -   Scenario 0: A C/U Split is not yet configured via the pico base        station 5-2. However, the frequency used by the pico base        station 5-2 is near an ISM frequency and the mobile device 3 has        already indicated interference problem relating to that        frequency.    -   Scenario 1: The macro base station 5-1 provides the C-plane        functionality and the pico base station handles the U-Plane        traffic for the mobile device 3 (i.e. there is no user bearer        via Macro cell). The frequency used by the pico base station 5-2        is near an ISM frequency.    -   Scenario 2: The macro base station 5-1 provides the C-plane        functionality and handles at least one user plane bearer, e.g.        Voice over IP (VoIP) or other high Quality of Service (QoS)        bearer. The pico base station handles the other U-Plane traffic        for the mobile device 3. The frequency used by the pico base        station 5-2 is near an ISM frequency.    -   Scenario 3: The macro base station 5-1 provides the C-plane        functionality and the pico base station handles U-Plane traffic        for the mobile device 3. The frequency used by the macro base        station 5-1 is near ISM frequency.    -   Scenario 3a: The macro base station 5-1 provides both the        C-plane and the U-Plane functionalities for the mobile device 3        (no C/U Split has been configured initially). The frequency used        by the macro base station 5-1 is near ISM frequency.    -   Scenario 4: The macro base station 5-1 provides C-plane        functionality and handles at least one user plane bearer, e.g.        VoIP or other high QoS bearer. The pico base station 5-2 handles        other U-Plane traffic for the mobile device 3. The frequency        used by the macro base station 5-1 is near ISM frequency.    -   Scenario 5: Both the frequency used by the macro base station        5-1 and the frequency used by the pico base station 5-2 are near        one or more ISM frequencies (e.g. band 7 and/or band 40).

In the following, with reference to FIG. 8, possible solutions aredescribed for each interference scenario mentioned in the above list.

Scenario 0

In the case when a C/U Split has not been configured for a particularmobile device 3 yet, the base stations 5 and the mobile device 3 canadvantageously alleviate interference as follows:

1) The mobile device 3 informs the macro base station 5-1 about its IDCcapability, (e.g. during registration with that macro base station 5-1)(step S800). Although not shown in FIG. 8, the macro base station 5-1also has also obtained information relating to the operation of itsneighbouring base stations (e.g. during an X2 setup procedure betweenthem), including the pico base station 5-2.

2) The macro base station 5-1 configures the ‘idc-config’ settings forthe mobile device 3 (step S801). The macro base station 5-1 takes intoaccount any previously received IDC indication and any informationrelating to the operating frequency of the pico base station 5-2 (i.e.on a frequency (such as Band 7 and Band 40) near to ISM band). Sincetheir respective E-UTRA Absolute Radio Frequency Channel Numbers(EARFCNs) have already been exchanged during the initial setup of the X2interface between the base stations 5, there is no need to exchange newinformation between the base stations 5 in order to determine whether ornot there is an IDC problem.

Since C/U Split has not yet been configured for this mobile device 3,step S802 has not yet been performed in this scenario.

3) The macro base station 5-1 receives an IDC indication (e.g. in an‘RRC: IDC Indication’ message) from the mobile device 3 indicating thatthe frequency used by the pico base station 5-2 suffers frominterference (step S803). The mobile device 3 may generate and send suchindication when, for example, the ‘idc-config’ settings provided by themacro base station 5-1 did not sufficiently alleviate the IDCinterference experienced (for example, arising from interference thathas, in effect, not yet been indicated).

4) Using the information available to it, the macro base station 5-1determines the best course of action, such as, for example:

-   -   preventing configuration of C/U-split for this mobile device 3        (if an FDM solution is to be used);    -   choosing another cell operating at a different frequency for        configuring the C/U split for this mobile device 3 (when a        different FDM solution is to be used);    -   applying a TDM solution (discussed in more detail below for        scenario 1).

If the macro base station 5-1 is already in the process of configuring aC/U-split for this mobile device 3 (e.g. if steps S802 and S803 areperformed substantially concurrently) then it may decide to terminatethe C/U split procedure and choose a different strategy from the aboveoptions.

5) The macro base station 5-1 (possibly involving the mobile device 3and/or the pico base station 5-2) handles the indicated interference(step S805) according to the course of action selected in step S804.Further, if the macro base station 5-1 determines that it is beneficial(or possible) to do so, it configures a C/U Split for the mobile device3 (step S806), when appropriate, also taking into account anyinformation available to it.

Scenarios 1 and 2

In this case, C/U Split is in place and interference has arisen on afrequency used by the pico base station 5-2, regardless whether or notthe macro base station 5-2 is also providing a user plane connection forthe mobile device 3. In this case, the following approach may be used:

Steps 1) and 2) (i.e. steps S800 and S801 of FIG. 8) are the same asdescribed for scenario 0 above.

3) The macro base station 5-1 configures the C/U Split for the mobiledevice 3 without being aware of a potential interference on the selectedpico base station's 5-2 band (step S802).

4) When IDC interference is detected by the mobile device 3, which itcannot solve by itself, the mobile device 3 generates and sends an IDCindication (e.g. and ‘RRC: IDC Indication’ message) to the macro basestation 5-1 (step S803).

5) The macro base station 5-1 selects an appropriate IDC solution (stepS804):

-   -   FDM solution—the macro base station 5-1 selects another small        cell upon receipt of an IDC indication for the currently used        small cell:        -   hand over the user plane connection from the current pico            base station 5-2 to a different pico base station operating            on a different frequency (e.g. based on associated EARFCN            obtained during X2 setup) than the frequency used by the            current pico base station 5-2;        -   instead of handing over the user plane connection, the macro            base station 5-1 may simply release the user plane bearer at            the current pico base station 5-2 and (re-)establish it via            a different pico base station (which may be selected, e.g.            using EARFCN or the like);        -   hand over the user plane connection to a cell of the macro            base station 5-1 (i.e. combine the user plane and control            plane bearers whilst also ensuring service continuity for            user plane traffic);        -   release the user plane bearer at the pico base station 5-2            and (re-) establish it via a cell of the macro base station            5-1 (i.e. combine the user plane and control plane bearers            without ensuring service continuity for user plane traffic).    -   TDM solution—the macro base station 5-1 maintains the user plane        connection via the current small cell upon receipt of an IDC        indication but changes the timing of user plane transmissions in        that cell, according to the following possibilities:        -   The macro base station 5-1 may configure an ‘autonomous            denial rate’ for the mobile device 3 to be applied for its            communications via the pico base station 5-2. Generally,            autonomous denial rate (as specified in 3GPP TS 36.331)            defines a number ‘x’ of sub-frames per a number ‘y’ of            sub-frames that the mobile device 3 is allowed to skip even            if resources have been scheduled for transmissions by that            particular mobile device 3. The value of ‘x’ may be selected            from the set {2, 5, 10, 15, 20, 30} and the value of ‘y’ may            be selected from the set {200, 500, 1000, 2000}. By skipping            scheduled (and hence expected) LTE transmissions, the mobile            device 3 is able to carry out non-LTE transmissions without            interference (as the LTE and non-LTE communications do not            happen at the same time). Autonomous denial can thus            mitigate the effects of IDC interference, but only up to the            limit defined by the autonomous denial rate configured for            the mobile device 3. Further, the autonomous denial rate is            typically applied for all communications by the mobile            device 3. In this case, however, the macro base station 5-1            advantageously configures the mobile device with an            autonomous denial rate specific to transmissions over the            cells of the pico base station 5-2. This approach makes it            possible for the mobile device 3 to communicate over the            (problematic) frequency used in the pico base station's 5-2            cell without violating its existing autonomous denial rate            configuration (which it would still apply to communications            via other base stations than the pico base station 5-2).        -   The macro base station 5-1 may use TDM assistance            information provided by the mobile device 3. Since the DRX            configuration (i.e. settings for periodically switching off            the mobile device's 3 transceiver circuit 301, usually to            save energy, but in this case to mitigate the effects of            interference) and/or the Hybrid Automatic Retransmission            reQuest (HARQ) configuration (i.e. the settings which enable            error correction to be adapted dynamically depending on            channel quality) are under the control of the pico base            station 5-2, the mobile device 3 is not configured to            provide such information to the macro base station 5-1. In            this case, however, the macro base station 5-1 may            advantageously obtain the TDM assistance information from            the pico base station 5-2 and take it into account when            configuring that particular mobile device 3. This allows            solving the interference problem without requiring direct            communication of the TDM assistance information between the            mobile device 3 and the macro base station 5-1 (which might            not be feasible anyway since this type of information is            usually exchanged using the bearer to which it applies, i.e.            in this case the bearer(s) between the mobile device 3 and            the pico base station 5-2). The macro base station 5-1 may            identify the appropriate TDM assistance information to be            used (from all the TDM assistance information available to            it) by comparing the frequency(-ies) reported by the mobile            device 3 (i.e. in the IDC assistance information) to the            frequencies used by its neighbours, including the pico base            station 5-2 which the IDC assistance relates to in this            scenario.

Although in this scenario there is no interference problem for thefrequency used in the macro base station's 5-1 cell, and hence no IDCrelated configuration and/or reporting is carried out between the macrobase station 5-1 and the mobile device 3 (i.e. step S803 is receivedindirectly, via the pico base station 5-2), the macro base station 5-1is still able to determine an appropriate course of action (in stepS804) and carry out configuration of IDC parameters for the bearers ofthe pico base station 5-2 carrying user plane communications for thatmobile device 3 (in step S805). If the macro base station 5-1 determinesthat it is beneficial to do so, it is able to reconfigure the C/U Splitfor the mobile device 3 (step S806), also taking into account any of theabove information.

Scenario 3

In this case, interference has arisen on a frequency used by the macrobase station 5-1. In this case, the following approach may be used:

The first two steps (i.e. steps S800 and S801 of FIG. 8) are the same asdescribed for scenario 0 above. Subsequently, the macro base station 5-1configures C/U Split for the mobile device 3 (step S802).

Consequently, the macro base station 5-1 provides the control plane andthe pico base station 5-2 provides the user plane for the mobile device3 at the time when interference is detected by the mobile device 3 onthe frequency used by the macro base station 5-1.

In this case, the mobile device 3 may advantageously deny ISMtransmissions whenever it needs to send RRC signalling, such as when itprovides IDC indication. Therefore, the mobile device 3 is able totransmit the necessary IDC indication to the macro base station 5-1(step S803), even though the interference is detected for the frequencythat is used for this transmission. Further, even if the mobile device 3is communicating via the user plane, in this case there is no need toprovide (direct) IDC indication to the pico base station 5-2 whichprovides the mobile device's 3 user plane connection. Unnecessarilydisruptions to user plane communications can therefore be avoided.

The macro base station 5-1 may determine the appropriate course ofaction to avoid the indicated interference based in the received IDCindication (step S804) and configure the mobile device 3 appropriately(step S805), e.g. by applying a TDM solution to the macro cell only.

Scenario 3a

In this case, the macro base station 5-1 provides all configuredcommunication bearers (both control plane and user plane). In this case,the IDC indication is received (in step S803) before a C/U Split isconfigured for the mobile device 3 (i.e. before step S802 is performed).

In this scenario, since the macro base station 5-1 is able to determine(in step S804) from the received IDC indication (and the informationshared with its neighbours) that the selected pico base station 5-2 isnot affected by the indicated IDC situation. Therefore, the macro basestation 5-1 configures a C/U Split for the mobile device (steps S805 andS806). This advantageously ensures that the mobile device 3 needs tosend only RRC signalling (a relatively small amount of data) over thecarrier (macro cell) experiencing interference and send user plane dataover a carrier of the pico base station 5-2 (which has not beenindicated to suffer from interference).

For the cell(s) of the macro base station 5-1, the solutions presentedfor scenario 3 also apply.

Scenario 4

In this case, interference has arisen on a frequency used by the macrobase station 5-1, which provides both control plane communications andat least part of the user plane communications for the mobile device 3.

In this case, traffic over the macro cell may be higher than in case ofscenario 3. However, the mobile device 3 is still able to deny ISMtransmissions while it is transmitting (or receiving) voice packetsand/or RRC signalling. Therefore, the solutions described for scenarios3 and 3a also apply for scenario 4.

Scenario 5

In this case, the frequencies used by both the macro base station 5-1and the pico base station 5-2 are suffering interference. This mayhappen, for example, when the base stations 5 use frequency bands (e.g.LTE band 7 and/or LTE band 40) near the ISM frequency bands.

In this scenario, both control plane and user plane communications forthe mobile device 3 would be disturbed by the interference, regardlesswhether or not C/U Split has been configured.

In this exemplary embodiment, the mobile device 3 is configured toreport TDM assistance information for the Scell in addition to reportingsuch information for the Pcell. In order to do this, two sets ofdiscontinuous reception configuration (‘drx-config’) parameters (e.g. a‘drx-config-r11_Pcell’ and a ‘drx-config-r11_Scell’) are provided (e.g.in response to an indicated IDC situation) to the mobile device 3 sothat it can use different configurations for the macro cell and thesmall cell, if necessary. Having a dedicated respective TDMconfiguration associated with the Pcell and with the Scelladvantageously allows the mobile device 3 to mitigate the effects of theIDC interference.

Accordingly, notwithstanding that this is a relatively uncommonscenario, this provides a distinct benefit over a system in which themobile device reports TDM assistance information for the macro cell only(which is not applicable for the small cell even though, in thisscenario, the macro cell and the small cell exist on the same carrier oron adjacent carriers).

The macro base station 5-1 and the pico base station 5-2 maintainsynchronisation of the above parameters between each other (e.g. as partof the X2 communication procedures between them).

MODIFICATIONS AND ALTERNATIVES

A detailed exemplary embodiment has been described above. As thoseskilled in the art will appreciate, a number of modifications andalternatives can be made to the above exemplary embodiment whilst stillbenefiting from the inventions embodied therein.

In the above exemplary embodiment, a mobile telephone basedtelecommunications system was described. As those skilled in the artwill appreciate, the reporting and interference avoidance techniquesdescribed in the present application can be employed in othercommunications system. Other communications nodes or devices (bothmobile and stationary) may include user devices such as, for example,personal digital assistants, smartphones, laptop computers, webbrowsers, etc.

In the above exemplary embodiments, a number of software modules weredescribed. As those skilled will appreciate, the software modules may beprovided in compiled or un-compiled form and may be supplied to the basestation or to the mobile device as a signal over a computer network, oron a recording medium. Further, the functionality performed by part orall of this software may be performed using one or more dedicatedhardware circuits. However, the use of software modules is preferred asit facilitates the updating of base station 5 and the mobile device 3 inorder to update their functionalities.

In the above examples, the Radio Access Technologies employed by thebase stations 5 operate according to either Frequency Division Duplexing(FDD) mode or Time Division Duplexing (TDD) mode. However, it will beappreciated that the base stations 5 might also operate according to anyother suitable technique.

In the above exemplary embodiments, the concurrent LTE and non-LTEcommunications are carried out by the same mobile device 3. However,whilst the above exemplary embodiments have particular benefit foralleviating in device coexistence interference issues, it will beappreciated that some aspects of the invention may be employed toalleviate interference in situations where one mobile devicecommunicates using the LTE RAT and another but separate device in thevicinity communicates using a non-LTE radio technology.

In the above exemplary embodiments, the mobile device 3 comprisesseparate LTE, GNSS, and ISM baseband circuits 300 a to 300 c. Eachbaseband circuit 300 a to 300 c is coupled to its own radio frequencytransceiver circuit 301 a to 301 c and uses its dedicated antenna 303 ato 303 c. It will be appreciated that some or all of the basebandcircuits 300 a to 300 c, some or all of the transceiver circuits 301 ato 301 c, and some or all of the antennas 303 a to 303 c might becombined in one component. Alternatively, the mobile device 3 mightemploy separate circuits and/or separate transceivers and/or separateantennas for each type of RAT that it supports. For example, althoughboth Bluetooth and Wi-Fi are ISM radio access technologies, some mobiledevices implement these standards using separate circuits and/orseparate transceivers and/or separate antennas. It is also possible thata given RAT requires more than one antenna or uses a separatetransmitter and/or receiver part. It is also possible that in additionto the LTE functionality, some mobile devices implement GNSSfunctionality only, whilst other mobile devices might implement ISMfunctionality only.

The exemplary embodiments have been described using ISM transceivers asan example of non-LTE radio technologies. However, the mechanismsdescribed herein can be applied to other non-LTE radio technologies(e.g. GNSS).

List of ISM technologies:

-   -   Bluetooth devices;    -   Cordless phones;    -   Near field communication (NFC) devices;    -   Wireless computer networks, such as HIPERLAN, Wi-Fi (IEEE        802.11);    -   Wireless technologies based on IEEE 802.15.4, such as ZigBee,        ISA100.11a, WirelessHART, and MiWi.

List of GNSS technologies:

-   -   Global or regional satellite navigation systems, such as GPS,        GLONASS, Galileo, Compass, Beidou, DORIS, IRNSS, and QZSS;    -   Global or regional Satellite Based Augmentation Systems, such as        Omnistar, StarFire, WAAS, EGNOS, MSAS, and GAGAN;    -   Ground based augmentation systems, such as GRAS, DGPS, CORS, and        GPS reference stations operating Real Time Kinematic (RTK)        corrections.

In the above exemplary embodiments, the IDC assistance information havebeen described as indicating either one of an interference relating tothe control plane, an interference relating to the user plane, a cellexperiencing interference, a frequency band experiencing interference,whether any autonomous corrective actions have been applied by themobile device. It will be appreciated that the assistance informationmight include, or be obtained from, any of the following informationtypes or any combination of these as well:

-   -   current interference level    -   maximum allowed interference level    -   mean interference level    -   indication of a type of non-LTE RAT being used    -   indication of a type of non-LTE RAT suffering interference    -   indication of a non-preferred RAT mode    -   indication of a preferred RAT mode    -   ISM duty cycle    -   ISM channels being used    -   LTE carrier frequency band(s) and/or sub-carrier(s) suffering        interference    -   LTE carrier frequency band(s) and/or sub-carrier(s) not        suffering interference    -   level of interference across a number of LTE carrier frequency        band(s) and/or sub-carrier(s)

In the above exemplary embodiments, the interference issues have beendescribed with respect to one device operating both the LTE and theISM/GNSS transceivers. However, it will be appreciated that theexemplary embodiments are applicable to interference issues involvingmultiple devices, e.g. one device operating an LTE transceiver andanother device operating an ISM or a GNSS transceiver. The exemplaryembodiments are also applicable to mobile devices which do not have anyongoing LTE transmissions (but e.g. their ISM or GNSS transmissionsuffers from interference) and which employ LTE signalling only for theduration of sending assistance information to a serving base stationwhich is able to manage the interference.

At the discussion of step S803, the IDC indication was embedded in an“InDeviceCoexistence” RRC signalling message. Alternatively, the IDCindication might be sent using a different signalling message.

In the above description of scenario 5, the ‘drx-config-r11_Pcell’ and‘drx-config-r11_Scell’ information elements are used for the macro celland the small cell, respectively. However, it will be appreciated thatdifferent information elements might be used, for example‘drx-config-r12_Pcell’ and ‘drx-config-r12_Scell’, respectively.Alternatively, ‘drx-config-r8_Pcell’ and ‘drx-config-r11_Scell’ might beused, thus maintaining compatibility in the macro cell for legacy userequipment.

Although not shown in FIG. 7, in some cases the user plane connectionmay be routed between the pico base station 5-2 and the core network 7(e.g. SGW 12) via the macro base station 5-1, i.e. using the X2interface provided between them. However, in this case a so-called‘ideal backhaul’ connection might be required between the macro basestation 5-1 and the pico base station 5-2 in order to ensure smoothoperation (i.e. very high throughput and very low latency). Thespecifications of an ‘ideal backhaul’ can be found in section 6.1.3 of3GPP TR 36.932 (v.12.1.0), the contents of which are incorporated hereinby reference.

In accordance with the above, therefore, the macro base station maytrigger consolidation of already split user plane (bearers) under itsown control in cases where e.g. the pico frequency experiences ISM, andthe pico base station does not support a TDM solution. The macro andpico base station may provide reconciled parameters for autonomousdenial and TDM configuration to the UE and UE may then comply with theseconfigurations for each bearer. The UE may provide assistanceinformation for both macro and pico cell bearers. The macro base stationmay be provided with information to allow it to determine if the picobase station supports a TDM solution, autonomous denial etc.

It will be appreciated that pico cell related parameters, such as itsability to support a TDM solution, autonomous denial etc, may beprovided by the UE to the macro base station or by the MME to the macrobase station. This information may be sent via user plane.

The macro and pico base stations may be able to exchange the capabilityof a pico cell to support a TDM solution for an IDC problem directly.For example, a macro and pico base station may exchange:

-   -   idc-config (direction: pico base station to and from macro base        station) including, for example, the autonomous denial rate to        be sent from the pico base station to the macro base station and        the idc-config sent to the UE from the macro base station to be        informed to pico base station pico eNB;    -   UE IDC indication and tdm-assistance information (direction:        macro base station to the pico base station)    -   UE DRX config and subframe config (direction: macro base station        to and from the pico base station) Further details concerning        the information that may be exchanged between the macro base        station 5-1 and the pico base station 5-2 are described in more        detail in Table 1 below, whilst details of information that may        be exchanged between the network entities and the mobile device        3 are described in Table 2 below in more detail.

TABLE 1 Information to be exchanged between the macro base station 5-1and the pico base station 5-2 IE name Information Direction Pico IDCMacro eNB obtains information relating to Pico −> Macro capability PicoeNB's support for TDM solution and/or autonomous denial. directly: usingX2 signalling (e.g. “X2: Setup” message) indirectly: via O&M AutonomousParameters as defined in 36.331. Macro −> Pico denial parameters MacroeNB informs Pico eNB about Pico−> Macro autonomous denial parametersconfigured for the UE if Pico provides the user plane. Alternatively,Pico eNB informs its preferred autonomous denial parameters to Macro eNBand also to the UE. UE assistance UE reports assistance information (toMacro Macro −> Pico information eNB) for the small cell (operated by thePico Macro eNB may eNB). modify contents Macro eNB sends DRX andsubframe before sending pattern provided by the UE to Pico eNB. them toPico eNB drx-config_Scell Configuration may be selected by the Pico Pico−> Macro eNB in response to instruction to apply TDM solution; or MacroeNB may suggest parameters for approval by the Pico eNB. subframepatternConfiguration selected by Pico in response Pico −> Macro to apply TDMsolution

TABLE 2 Information to be exchanged between network entities and themobile device 3 IE name Information Direction drx-config-r11_PcellExisting drx-config-r11 could also be Network −> UE OR used for Pcellwithout any change in drx-config-r12_Pcell ASN.1 (ASN: abstract syntaxnotation used in encoding/decoding message contents sent over the airinterface) drx-config-r11_Scell IE comprising the same set of Network −>UE OR parameters as defined for ‘drx-config- drx-config-r12_Scell r11’but in this case for setting up IDC specific DRX for the Scell onlydrx-config_Scell (or Drx-config IE exists from Rel-8 and is Network −>UE Picocell) applicable per UE (for all its cells). In These above IEsOR this case, it is applied for the Pcell only. will allowdrx-config_Scell In case IDC DRX is configured for different DRX macroand normal Rel-8 DRX needs to configuration for be configured for Scell,new IE is Macro and Pico needed and we name it drx-config_scell celltdm- This IE allows the UE to report TDM UE −> NetworkassistanceinformationScell assistance information for the Scell (PicoeNB) subframepatternIndication This IE indicates if subframe pattern isNetwork −> UE for Pcell or Scell (or both). autonomousDenialParameters-Configuration parameters applicable for Network −> UE r11_Picocell (orScell) the small cell (Pico eNB) OR autonomousDenialParameters-r12_Picocell

Glossary of 3GPP Terms BT Bluetooth DRX Discontinuous Reception

eNB Evolved NodeB—base station

E-UTRA Evolved UMTS Terrestrial Radio Access E-UTRAN Evolved UMTSTerrestrial Radio Access Network FDM Frequency Division MultiplexingGNSS Global Navigation Satellite System GPS Global Positioning System

IDC interference avoidance for In Device CoexistenceISM Industrial, Scientific and Medical (radio bands)

LTE Long Term Evolution (of UTRAN) RAT Radio Access Technology RRC RadioResource Control RRM Radio Resource Management Rx Receiver SIR Signal toInterference Ratio TDM Time Division Multiplexing Tx Transmitter UE UserEquipment

DL Downlink—link from base station to mobile deviceUL Uplink—link from mobile device to base station

1. A method performed by user equipment (UE) configured to communicatewith a first base station and a second base station via a plurality ofcarriers using a first radio technology, which is an Evolved UniversalTerrestrial Radio Access (E-UTRA) radio technology, the plurality ofcarriers including a signalling radio bearer for communicating RadioResource Control (RRC) signalling between said UE and said first basestation, and configured to communicate with a wireless communicationdevice using at least one second radio technology, the methodcomprising: detecting in-device coexistence (IDC) interferencecorresponding to said second base station based on coexistence of theE-UTRA and the at least one second radio technology within said UE;sending to said first base station, in an RRC message via saidsignalling radio bearer, when the IDC interference is detected, an IDCindication including information identifying a type of the at least onesecond radio technology affected by the E-UTRA radio technology; whereinthe IDC interference is addressed based on allocation of at least onephysical resource block (PRB) within one of said plurality of carriersand outside a frequency range of the at least one second radiotechnology.
 2. A method performed by a first base station configured tocommunicate with user equipment (UE) via at least one of a plurality ofcarriers using a first radio technology, which is an Evolved UniversalTerrestrial Radio Access (E-UTRA) radio technology, the plurality ofcarriers including a signalling radio bearer for communicating RadioResource Control (RRC) signalling between said first base station andsaid UE, wherein the UE communicates with a second base station via atleast one of said plurality of carriers using said E-UTRA radiotechnology and communicates with a wireless communication device usingat least one second radio technology, the method comprising: receiving,from said UE, an in-device-coexistence (IDC) indication in an RRCmessage via said signalling radio bearer, when the UE detects an IDCinterference corresponding to said second base station based oncoexistence of the E-UTRA radio technology and the at least one secondradio technology in said UE, the IDC indication including informationidentifying a type of the at least one second radio technology affectedby the E-UTRA radio technology; and addressing said IDC interference byallocating at least one physical resource block (PRB) within one of saidplurality of carriers and outside a frequency range of the at least onesecond radio technology.
 3. User equipment (UE) comprising: at least onememory operable to store program instructions; at least one transceiver;and at least one processor operable to read said program instructionsand configured by the program instructions to: control said at least onetransceiver to: communicate with a first base station and a second basestation via a plurality of carriers using a first radio technology,which is an Evolved Universal Terrestrial Radio Access (E-UTRA) radiotechnology, the plurality of carriers including a signalling radiobearer for communicating Radio Resource Control (RRC) signalling betweensaid UE and said first base station; and communicate with a wirelesscommunication device using at least one second radio technology; detectin-device coexistence (IDC) interference corresponding to said secondbase station based on coexistence of the E-UTRA and the at least onesecond radio technology within said UE, and when the IDC interference isdetected, control said at least one transceiver to send, to said firstbase station, in an RRC message via said signalling radio bearer, an IDCindication including information identifying a type of the at least onesecond radio technology affected by the E-UTRA radio technology; whereinthe IDC interference is addressed based on allocation of at least onephysical resource block (PRB) within one of said plurality of carriersand outside a frequency range of the at least one second radiotechnology.
 4. A base station comprising: at least one memory operableto store program instructions; at least one transceiver; and at leastone processor operable to read said program instruction and configuredby the program instruction to: control said at least one transceiver tocommunicate with user equipment (UE) via at least one of a plurality ofcarriers using a first radio technology, which is an Evolved UniversalTerrestrial Radio Access (E-UTRA) radio technology, the plurality ofcarriers including a signalling radio bearer for communicating RadioResource Control (RRC) signalling between said base station and said UE,wherein the UE communicates with another base station via at least oneof said plurality of carriers using said E-UTRA radio technology andcommunicates with a wireless communication device using at least onesecond radio technology; receive, from said UE, an in-device-coexistence(IDC) indication in an RRC message via said signalling radio bearer,when the UE detects an IDC interference corresponding to said anotherbase station based on coexistence of the E-UTRA radio technology and theat least one second radio technology in said UE, the IDC indicationincluding information identifying a type of the at least one secondradio technology affected by the E-UTRA radio technology; and addresssaid IDC interference by allocating at least one physical resource block(PRB) within one of said plurality of carriers and outside a frequencyrange of the at least one second radio technology.
 5. A non-transitorycomputer readable medium comprising computer implementable instructionsfor causing a programmable device to perform the method of claim
 1. 6. Anon-transitory computer readable medium comprising computerimplementable instructions for causing a programmable device to performthe method of claim 2.